Don't cut the black wire!

Sometimes the obvious answer is staring you in the face.

I found that I had cut the ground wire to the G boards at some point. Why? I forget. The perils of stretching this project over so long is things like this slip your mind.
Anyway, I found the two ends tied together.

Knot what I was hoping to find

As for why I didn't check that the earth wire was connected to ground before, I can only say I need to think a bit harder!

I reconnected the earth to the G boards and the problem was solved. Just the faint hiss of old electronics was left.

G Board output connectors cleaned and ready to reconnect.

I set about reconnecting the outputs and all was well until I realised that I couldn't get any tones to come out anymore. Nothing from the clock dividers, nothing from the tone generators at all. Then I checked the power supply and the -26V rail had gone. Just that rail though. After checking the PSU (during which I managed to spike the ground and trip my whole house's power, even with an RCD connected!) I could see that the fuse for that line was blown. I replaced it but it just blew again. I disconnected the PSU from the boards and it then held up okay. I couldn't find any obvious shorts to ground - maybe there was something touching somewhere - but I'd run out of 500mA fuses, so I finished reconnecting the outputs and started stacking the G boards back together. During that I found a loose -26V wire too. Hmm!
I've ordered some more fuses so next I will reconnect that wire, test the connections for -26V, check for shorts again and then see if the issue has gone.

If that works then everything should be okay, finally. A fully working SS30 in a rack case without MIDI! And that means I can, at long last, start on the MIDI interface.

In the background I have been rethinking the front panel again. More, much more, on that to follow.